This invention relates generally to an air curtain-projecting ventilator, and more particularly to a ventilator whose rotor is provided with centrifugal vanes operating within the confines of an open-coil helix lining the tubular casing of a stator assembly having longitudinally extending intake and outlet slots to generate a uniform air curtain of high velocity.
In my prior U.S. Pat. No. 3,350,994 isued Nov. 7, 1967, there is disclosed a ventilating system which projects and air curtain by means of a tubular casing having a rotor mounted eccentrically therein, the rotor extending the full length of the casing and being provided with outstretched vanes or wings whose free edges are tracked to run adjacent to the inner surface of the casing. The casing is formed with a large intake opening and a narrow outlet parallel thereto, so that as air passes through the intake, it is collected by the vanes, compressed thereby and forced out through the outlet at great velocity.
This ventilator functions as an efficient centrifugal air pump to produce an air curtain which is fully effective throughout the entire length of the outlet. On the intake or suction side of the air pump, one may install heating, cooling, and air filter elements to condition the air.
Such air curtain-projecting ventilators have many practical applications and are useful wherever it is necessary to thermally or otherwise isolate a given region, such as the interior of a building from the exterior, without interposing a physical barrier in the entrance thereto. For example, where a working station is to be maintained in a clean atmosphere, one may use an air curtain to isolate this station from a surrounding contaminated atmosphere.
The difficulty experienced with a ventilating air pump structure of the type disclosed in my prior patent is that the intake and outlet slots formed in the casing constitute structural gaps in the support for the centrifugal blades of the rotor. Because of these gaps, it becomes necessary to track the vanes at their opposing ends to maintain the free edges of the vanes slightly spaced from the surface of the casing. However, because the vanes are subjected to centrifugal force and are retained only at their ends, they tend to bow and thereby strike the surface of the casing. The resultant knocking action of the vanes produces objectionable noise and degrades the efficiency of the system.
Another factor which has to a degree militated against the success of an air-curtain projecting air pump of the type disclosed in my prior patent is that the centrifugal blades, because of the bowing effect previously mentioned, make contact along their edges with the curved inner surface of the casing, thereby giving rise to a relatively high degree of friction and loss of operating efficiency.